The studies proposed herein investigate the feasibility of using high- frequency ultrasonic imaging to characterize and monitor the progressive articular cartilage degeneration associated with osteoarthritis. The approach provides a comprehensive investigation of the relationships between ultrasonic signal descriptors and the geometrical and biochemical properties of cartilage. Specific aims of the study are designed to examine ultrasonic attenuation, thickness, surface scattering, and internal scattering; and to correlate these descriptors with the cartilage water content, uronic acid concentration, thickness, and histologic appearance. Data processing algorithms will be developed to extract the ultrasonic descriptors from digitized A-mode signals and B-mode images obtained at frequencies of 25 MHz and 50 MHz. The relationship between ultrasonic measurements and histologic and biochemical properties will be examined by standard correlation and linear regression analysis and a nonparametric approach utilizing statistical pattern recognition. In vitro experiments with canine and human articular cartilage will examine the practically attainable tissue characterization capability, complexity of implementation, and overall feasibility of the approach. If the approach exhibits discrimination capabilities commensurate with clinical needs, a follow-up proposal will be devoted to the development of an arthrosonographic imaging probe for in vivo application.